CPR Spiral Tunnels - Field, British Columbia, Canada
Posted by: 
The A-Team
N 51° 25.880 W 116° 24.236
11U E 541436 N 5697961
This viewpoint looks down on one of the famous Canadian Pacific Railway spiral tunnels, where visitors can view trains passing over or under themselves, located on the side of the Trans-Canada Highway 7 km east of Field, British Columbia, Canada.
Waymark Code: WMN1B8
Location: British Columbia, Canada
Date Posted: 12/06/2014
Views: 11
When planning the route of the Canadian Pacific Railway in the early 1880s, officials had two possible locations where the railway could pass through the Rocky Mountains: Yellowhead Pass 200 km to the northwest, or here at Kicking Horse Pass. The original plan was to use Yellowhead Pass, but this was later discarded in favour of the more southerly route because it was more direct and was closer to the American border, which would help keep American railways from encroaching on the Canadian market.
One major disadvantage of the Kicking Horse Pass route was the terrain just west of the summit. In the first 6 kilometres west of the summit, the Kicking Horse River drops 350 metres. The narrow valleys and high mountains limited the areas where the railway could stretch out and reduce the grade. The original plan was to blast a 430-metre tunnel through Mount Stephen, which would allow for a 2.2% grade, but digging the tunnel would delay the completion of the railway by at least a year. A decision was made to delay construction of the tunnel and temporarily build the railway over the area, named Big Hill, in 1884. This overland route had a whopping 4.5% grade, over four times the recommended grade for railways of the time, making it the steepest rail line in North America at the time.
Due to the dangerously steep grade of Big Hill, three safety switches were installed to protect against runaway trains. Each switch led to a short spur line with a sharp uphill grade. As trains descended Big Hill, the switches were kept in the uphill spur position until the operator was satisfied that the approaching train was under control. Speed was also limited to 13 km/h for passenger trains and 10 km/h for freight trains, and elaborate brake testing was required before trains could attempt the descent. Even with these safety measures, disasters were frequent. In fact, the first train to attempt the hill in 1884 derailed, killing three workers.
The Big Hill route was intended to be temporary until the Mount Stephen tunnel could be built, but it remained "temporary" for 25 years. In 1906, John Edward Schwitzer, the senior engineer of CPR's western lines, undertook a project to improve the route through the Kicking Horse Pass. Options that were considered included building the rail line higher above Field on the south side of the Kicking Horse River valley, or extending the route up the Yoho River valley to increase the distance. However, problems with avalanches on other parts of the line persuaded Schwitzer that digging expensive spiral tunnels was the only viable option.
The route that was chosen called for a pair of three-quarter circle spiral tunnels in the valley walls, which opened on September 1, 1909. The higher tunnel, running under Cathedral Mountain, is 991-metres-long and the lower tunnel, running under Mount Ogden, is 891-metres-long. Both tunnels descend approximately 50 feet between their portals, allowing long enough trains to pass over or under themselves, depending on whether they're going uphill or downhill. With the addition of the tunnels and new track alignments on either end, 5.5 kilometres was added to the line and the grade was reduced to a much safer, though still challenging, 2.2%.
The viewpoint at this location looks down on the lower spiral tunnel. Since this is the CPR mainline and one of the only rail routes through the Rocky Mountains, trains are constantly passing through the area, so you don't have to wait long to see one. A video showing a train passing under itself can be seen
here.